CYANOBACTERIA AND CYANOBACTERIAL LICHENS FROM INSELBERGS OF THE IVORY-COAST, AFRICA

This study focuses on the saxicolous lichens and cyanobacteria of the open, exposed rock surface of inselbergs. Twenty-three species of cyan obacteria and 17 cyanobacterial lichen species (''cyanolichens'') from several inselbergs and other rocky outcrops of three major climatic r egions, savanna, transition zone and rain forest, are reported from th e Ivory Coast. Inselbergs are isolated and frequently mountains consis ting of Precambrian granites or gneisses that abruptly rise from the s urrounding plains. Cyanobacteria were found to be the dominating organ isms on all rock surfaces. The lichens found mainly belong to the fami ly Peltulaceae and a few were present from the family Lichinaceae. Nin e species of the cyanolichens and most of the cyanobacteria are new fo r the Ivory Coast. A gradient in total species number (cyanolichens an d cyanobacteria) occurs from the savanna to the rain forest, with a de crease in species number towards the rain forest. Saxicolous cyanobact erial lichens reached a higher species number in the savanna type ecos ystem (11) than on inselbergs in the rain forest (7). The cyanolichens and cyanobacteria found are characteristic for larger, light-exposed rock surfaces and species like P. congregata, P. lingulata, P. tortuos a and P. umbilicata preferentially occur on the granite or sandstone o f inselbergs.